In a conventional device for determining a constant of a rotating machine, e.g., as described in JP 2-304380 A (particularly, pp. 5-9, FIGS. 8-10) (hereinafter referred to as Patent Document 1), with an induction machine (rotating machine) using an inverter as a driving power source, the inverter output voltage is generated to produce a single-phase power-supply state or a power-supply state equivalent thereto, and the voltage and frequency, and the current flowing in the induction machine are substituted in an induction machine transfer function expression to obtain primary resistance, secondary resistance, primary self-inductance, secondary self-inductance, and mutual inductance.
Other conventional examples include that described in JP 6-273496A (particularly, pp. 4-9, FIGS. 1-5) (hereinafter referred to as Patent Document 2), for example. A three-phase voltage command signal is generated according to a d-axis voltage command, a q-axis voltage command, and a primary angular frequency command, and the output voltage of a power converter is controlled in proportion thereto and applied to the rotating machine. While the output current of the inverter is detected and d-axis and q-axis current components are detected according to the detected current and the primary angular frequency command, an AC signal is given as the value of the d-axis voltage command, with the values of the primary angular frequency command and the q-axis voltage command being zero. Next, according to the three-phase voltage command signal generated on the basis thereof, the converter output voltage is applied to the rotating machine. At this time, the d-axis current component flowing in the rotating machine is detected and the detected value is analyzed according to Fourier expansion based on trigonometric functions, using the AC signal as a reference, and constants of the rotating machine are obtained on the basis of Fourier coefficients for the fundamental wave component and the AC signal value.
Also, other conventional examples include that described in JP 7-55899 A (particularly, pp. 5-13, FIGS. 1-3) (hereinafter referred to as Patent Document 3), for example. A three-phase voltage command signal is generated according to a d-axis voltage command, a q-axis voltage command and a primary angular frequency command, and the output voltage of a power converter is controlled in proportion thereto and applied to the rotating machine. While the output current is detected and d-axis and q-axis current components are detected according to the detected current and the primary angular frequency command, an AC signal is given as the value of the d-axis voltage command, with the values of the primary angular frequency command and the q-axis voltage command being zero, and the converter output voltage is applied to the rotating machine according to the three-phase voltage command signal generated on the basis thereof. At this time, the d-axis current component flowing in the rotating machine is detected and the detected value is analyzed according to Fourier expansion, using the AC signal as a reference. In obtaining Fourier coefficients for the fundamental wave component, two frequencies are used about the AC signal, and constants of the rotating machine are obtained from the relation between the Fourier coefficients and current component values corresponding to the Fourier coefficients, obtained from the frequency characteristic of output current/input voltage in a rotating machine model.
All of the conventional devices for determining a constant of a rotating machine described above determine the constants by solving simultaneous equations corresponding to the number of unknown constants. Therefore, because of restrictions by the simultaneous equations, the number of times that the frequency of the alternating voltage is selected during a single-phase power supply is limited to twice or three times, and it is therefore not possible to repeatedly perform the test many times to obtain enhanced accuracy in determining the constants.
Also, because the conventional device for determining a constant of a rotating machine determines the constants with simultaneous equations about gains of rotating machines, it is not possible to obtain proper solutions of the equations in frequency bands where the gain is fixed, which places limitations on the alternating voltage frequency band during the single-phase power supply.
Also, while inductance values of rotating machines depend on current amplitude because of magnetic saturation, the above-described conventional devices for determining a constant of a rotating machine do not consider the current amplitude and so cannot determine inductance values required to actually drive the rotating machines.